Field of the Invention
The disclosure relates in general to a thermoplastic resin composition, more particularly to a thermoplastic resin composition with good physical properties.
Description of the Related Art
An impact-resist styrene-based resin composition formed by dispersing the rubber-containing graft copolymer in the styrene-based copolymer can be used to make a product with high impact strength. The resin composition has to go through several processing steps and mouldings (such as the primary processing including the injection moulding and the extrusion moulding, and the secondary processing such as the vacuum moulding) before obtaining a final product. Since the processing plants pay more attention to the easy-processing resin and the product with well physical properties and high impact strength, it is an important issue to be solved to develop a styrene based resin composition having physical properties in balance and also suitable for being widely applied to form various products.
Without sacrificing the physical properties of the product, it is known that small amounts of a slip agent (as a processing aid during molding) added into the rubber-modified polystyrene-based resin can enhance the flowability of the molding product in the processing, thereby improving the processability of the resin mold. Pentaerythritoltetrastearate is typically added in the rubber-modified polystyrene-based resin as the slip agent, and it does have effect on the processability of the resin; however, pentaerythritoltetrastearate would also lead to the resin residuals at the inlet gate of mold (ex: drawing phenomenon appears when the inlet port is away from to the inlet gate of mold), thereby forming the high gate scar of resin correspondingly. It requires one more extra step to remove the resin residuals. Alternatively, N,N′-ethylene bisstearamide is also one of the slip agents commonly used in the resin. Although adding N,N′-ethylene bisstearamide in the rubber-modified polystyrene-based resin does improve the processability of the resin, it leads to the poor demoulding of the resin. If the injection pressure of the injector for pumping the resin is not under a well-controlled, it would be easy to induce whitening portions at the surface of the product during demoulding, which restricts the processing range of the demoulding (i.e. small workable range).
Thus, it is one of important goals for the manufactures to develop a styrene based resin composition having physical properties such as good processing property and good demoulding property in balance.